<template>
  <div class="xtx-pagination">
    <a @click="changePager(myCurrentPage - 1)" v-if="myCurrentPage > 1" href="javascript:;">上一页</a>
    <a v-else href="javascript:;" class="disabled">上一页</a>
    <span v-if="pager.start > 1">...</span>
    <a @click="changePager(i)" href="javascript:;" v-for="i in pager.btnArr" :key="i"
      :class="{ active: i === myCurrentPage }">{{ i }}</a>
    <span v-if="pager.end < pager.pageCount">...</span>
    <a @click="changePager(myCurrentPage + 1)" v-if="myCurrentPage < pager.pageCount" href="javascript:;">下一页</a>
    <a v-else href="javascript:;" class="disabled">下一页</a>
  </div>
</template>
<script setup >
import { computed, ref, watch } from 'vue'

const props = defineProps({
  total: {
    type: Number,
    default: 100
  },
  pageSize: {
    type: Number,
    default: 10
  },
  currentPage: {
    type: Number,
    default: 1
  }
})
const emit = defineEmits(["currentChange"])
// 需要数据：
// 1. 约定按钮的个数 5 个，如果成为动态的需要设置响应式数据
const count = 5
// 2. 当前显示的页码
const myCurrentPage = ref(1)
// 3. 总页数 = 总条数 / 每一页条数  向上取整
const myTotal = ref(100)
const myPageSize = ref(10)

const pager = computed(() => {
  // 总页数
  const pageCount = Math.ceil(myTotal.value / myPageSize.value)
  // 按钮个和当前页码 ====> 起始按钮，结束按钮，按钮数组
  // 1. 理想情况下：
  const offset = Math.floor(count / 2)
  let start = myCurrentPage.value - offset
  let end = start + count - 1
  // 2. 如果起始页码小于1需要处理
  if (start < 1) {
    start = 1
    end = (start + count - 1) > pageCount ? pageCount : (start + count - 1)
  }
  // 3. 如果结束页码大于总页数需要处理
  if (end > pageCount) {
    end = pageCount
    start = (end - count + 1) < 1 ? 1 : (end - count + 1)
  }

  const btnArr = []
  for (let i = start; i <= end; i++) {
    btnArr.push(i)
  }
  // 提供计算属性数据
  return {
    pageCount,
    btnArr,
    start,
    end
  }
})

// 监听props的变化，更新组件内部数据
watch(props, () => {
  myTotal.value = props.total
  myPageSize.value = props.pageSize
  myCurrentPage.value = props.currentPage
}, { immediate: true })

// 切换分页函数
const changePager = (page) => {
  // 页码相同不作为
  if (myCurrentPage.value !== page) {
    myCurrentPage.value = page
    // 通知父组件
    emit('currentChange', page)
  }
}

</script>
<style scoped lang="less">
.xtx-pagination {
  display: flex;
  justify-content: center;
  padding: 30px;

  >a {
    display: inline-block;
    padding: 5px 10px;
    border: 1px solid #e4e4e4;
    border-radius: 4px;
    margin-right: 10px;

    &:hover {
      color: @xtxColor;

    }

    &.active {
      background: @xtxColor;
      color: #fff;
      border-color: @xtxColor;

    }

    &.disabled {
      cursor: not-allowed;
      opacity: 0.4;

      &:hover {
        color: #333
      }
    }
  }

  >span {
    margin-right: 10px;
  }
}
</style>
